Gliederung

Purpose: To evaluate the effect of the average and variability of heart rate on the image quality with 64-slice MDCT coronary angiography.

Materials and Methods: 125 patients (45 women, 80 men; mean age 59.9 Â± 12.9 years) underwent 64-slice coronary CT angiography. MDCT data sets of the heart were reconstructed in 5% steps from 20 to 80% of the R-R interval. The ECG was digitally recorded and the variability of heart rate during scan was identified by calculating the standard deviation of the average heart rate for each patient. Two observers rated the image quality from 1 (no motion artifacts) to 5 (unassessable) for each coronary segment with a diameter of more than 1.5 mm. Image quality was correlated to the average heart rate and the heart rate variability during MDCT scan.

Results: Diagnostic image quality (score Â£ 3) was present in more than 99% of all coronary segments (1860/1875) when using the best reconstruction interval. The average heart rate was 63.3 Â± 13.1 beats per minute (range 38 - 102) and the heart rate variability was 3.2 Â± 2.1 (range 0.5 - 9.7). Overall image quality (mean 1.60 Â± 0.59) did not significantly correlate with average heart rate (r = 0.25; p = ns), but significantly correlated with variability of heart rate during scan (r = 0.75; p < 0.05). Seventy-four patients had b blockers as part of their baseline medication. In these patients, heart rate was significantly more regular during scan compared with patients without b blocker, and overall image quality was significantly improved (p < 0.05). At heart rate < 75 bpm best image quality was mostly achieved in diastole, while in higher heart rate the reconstruction time point for best image quality shifted to systole.

Conclusions: In contrast to the average heart rate, reducing variations of the heart rate during scan by b blockers significantly improves image quality of coronary CT angiography with 64-slice CT.